1. Field of the Invention
This invention relates to physical exercise apparatus for use in developing human muscles.
2. Prior Art
The human body has a substantial number of muscle groups and in the past various types of mechanical exercise equipment have been used to increase both muscular strength and size. However, many prior exercise devices have been either relatively complex, expensive, or limited in versatility and efficiency in terms of the number of muscle groups an individual apparatus could adequately develop.
Prior devices have often utilized cams, pulleys, levers or frictional mechanisms to provide a resistance force against which muscular training could be accomplished. But all such devices have been inadequate in providing a resistance curve most suitable for rapid and efficient muscular development.
Physiological studies have shown that in most cases power output (strength) exerted by the human limbs or trunk, actually increases as these limbs or trunk approach positions of full extension or flexion, due to the unique interactions of muscular strength curves and skeletal leverage, and that maximal contraction of muscle fiber occurs when a muscle is sustained in a static, or isometric, contractile state.
Therefore, throughout the range of an exercise movement, resistance should, in most cases, actually steadily increase against the contracting muscle(s), and a static, or isometric, contraction should be experienced within the terminal range of the movement.
Designers of prior exercise equipment have failed to recognize this principle and have provided resistance curves, inadequate in terms of generating maximum contraction of muscle fiber at the position of greatest musculoskeletal strength advantage.
Even most elaborate training devices, using expensive systems of cams and gears, and which provide a variable resistance to approximately match a muscles' strength curve, fail to provide the necessary static, or isometric, resistance within the range of greatest musculoskeletal strength advantage.
Other types of apparatus, namely gravitationally influenced barbells and dumbells, produce a resistance that may actually decrease as the exercised bodypart approaches its position of greatest strength output.
With some apparatus, such as fixed pulley/cable systems, a constant resistance is at least provided, but an unwanted mechanical advantage may be introduced due to an incorrect angle of pulling or tugging, namely that the moment arm has changed incorrectly.